Chronic inflammation is increasingly being recognized as contributing to a wide array of diseases but systemic administration of immunosuppressive agents is limited by significant off-target effects. There is a need for more targeted anti-inflammatory therapies. DCs are ideal targets given their critical role in regulating immunity and cellular therapy with in vitro generated tolerogenic DCs (tDCs) showing great promise in treating inflammation. Targeted induction of inflammation-resistant tDCs is limited both by our understanding of tDCs and ability to generate these tDCs in vivo during inflammatory disease. We have found that the pregnancy-specific hormone estriol (E3) generates tDCs that protect against experimental autoimmune encephalomyelitis (EAE), an animal model for chronic inflammatory and demyelinating disease multiple sclerosis (MS). Of therapeutic importance, E3 protects MS patients from relapses and E3 tDCs limit disease in the face of inflammatory challenge. We hypothesize that E3's protective effects are mediated largely due to induction of tDCs that suppress pathogenic inflammatory immune responses. In this proposal, we investigate the targeted induction of tDCs in vivo using newly developed microparticles (MPs) encapsulating E3 (Specific Aim 1). Additionally, given that the therapeutic use of tDC to treat inflammatory disease is limited by our understanding of mechanisms involved in tDC induction, we will investigate the estrogenic signaling pathways involved in the induction of tDCs (Specific Aim 2). The application of such MP technology for targeted tDC induction and a better understanding of signaling pathways critical for the induction of tDCs have direct therapeutic applications in numerous immune-mediated, autoimmune and chronic inflammatory diseases. PUBLIC HEALTH RELEVANCE: Experimental autoimmune encephalitis (EAE) is a disease model for multiple sclerosis, for which there is no cure. The induction of tolerogenic DCs (tDC) is an exciting new approach for the treatment of this and other inflammatory diseases. Currently, this approach is limited by our understanding of tDCs and by the ability to generate these tDCs in vivo during inflammatory disease. Our studies show that estriol (E3), generates tDCs, which protect mice from inflammatory EAE. In this proposal, we use newly developed micro particles (MPs) encapsulating E3 to induce tDCs in vivo to treat inflammatory disease EAE and investigate the signaling mechanisms involved in E3 tDC induction. The use of such MP technology and a better understanding of signaling pathways critical for tDCs induction has direct therapeutic applications in numerous immune- mediated, autoimmune and chronic inflammatory diseases.